As shown in FIG. 25, a conventional pipe joint construction includes a first mounting groove 3 formed in an inner circumferential surface 1a of a receiving pipe section 1 for receiving an elastic seal member 4 to hermetically seal between the inner circumferential surface 1a of the receiving pipe section 1 and an outer circumferential surface 2a of an inserted pipe section 2, a stopper wall portion 6 formed at a portion close to an receiving opening from the mounting groove for limiting a maximum contracting position between the pipe sections 1 and 2 by contacting an annular engaging projection 5 protruding from the outer circumferential surface 2a of the inserted pipe section 2 in a pipe axis direction X, a second mounting groove 51 for receiving a substantially C-shaped lock member 50 elastically deformable in a diameter-increasing direction, and cum faces 52 and 53 formed on corners, opposing to each other in the pipe axis direction X, of the engaging projection 5 of the inserted pipe section 2 and the lock member 50 attached to the second mounting groove 51 for elastically deforming the lock member 50 in the diameter-increasing direction to the point of defining an inner diameter allowing passage of the inserted pipe section 2 as it is inserted into the receiving pipe section 1. (see Japanese unexamined patent publication “Kokai” No. 9-303636)